Put about 1 inch (3 cm) of salted water in a large pot-use clean seawater if you have access to it. Bring the water to a boil and add the lobsters. Return to the boil and simmer tightly covered until done: 10 minutes for 1 lb lobsters; 13 minutes for 1 1/4 lb lobsters; 15 minutes for 1 1/2 lb lobsters; 18 minutes for 2 lb lobsters. The lobsters are done when they're bright red in color and when the antennae can be removed with a sharp tug. If in doubt, tear one of the tails from the lobster-it is done if the exposed flesh is opaque with no translucency. Meanwhile, combine the melted butter and lemon juice and place into small bowls. Transfer the lobsters to serving plates and serve with lemon butter and lemon wedges.